Early Diagnosis of Acute Myocardial Infarction in Patients With Pre-Existing Coronary Artery Disease Using More Sensitive Cardiac Troponin Assays
What is the impact of high-sensitivity troponin (hs-Tn) measurements on the diagnosis of acute myocardial infarction (AMI) in patients with pre-existing coronary artery disease (CAD) presenting with chest pain?
The diagnostic accuracy of three sensitive cardiac Tn (cTn) assays was tested in 1,098 patients presenting with symptoms suggestive of AMI, of whom 37% had pre-existing CAD.
AMI was determined to be the final diagnosis in 19% of CAD patients. In those without AMI, baseline cTn levels were elevated above the 99th percentile with Roche hs-cTnT in 40%, with Siemens TnI-Ultra in 15%, and Abbott-Architect cTnI in 13%. The diagnostic accuracy at presentation was significantly greater for the sensitive cTn assays compared with the standard assay (area under the curve [AUC] for Roche hs-cTnT, 0.92; Siemens cTnI-Ultra, 0.94; and Abbott-Architect cTnI, 0.93 vs. AUC for the standard assay, 0.87; p < 0.01 for all comparisons). Elevated levels of cTn measured with the sensitive assays predicted mortality irrespective of pre-existing CAD, age, sex, and cardiovascular risk factors.
The authors concluded that sensitive cTn assays have high-diagnostic accuracy in CAD patients. Mild elevations are common in non-AMI patients, and test-specific optimal cut-off levels tend to be higher in CAD patients than in patients without history of CAD. Sensitive cTn assays also retain prognostic value.
The speed and accuracy of managing chest pain patients may be improved with higher-sensitivity cTn assays, as this and previous studies imply. However, 40% of patients with CAD deemed not to have AMI in this study showed cTn levels above the 99th percentile using the most sensitive assay. Determination of the optimal cut-off values and the net clinical benefit (outcomes and cost savings) of these assays will need to be addressed in future studies. The long-term prognostic implications of elevated cTn, even in patients without acute coronary syndrome, are particularly interesting, and may be useful in guiding preventive therapies. Further study is required.
Keywords: Coronary Artery Disease, Acute Coronary Syndrome, Biological Markers, Early Diagnosis, Troponin
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